Many methods have been proposed for studying the cure kinetics of rubber compounds. Mechanical properties of rubber specimens are generally measured as a function of cure time. Decker, et al, Rubber Chem. Technol. 36, 451 (1963), developed an oscillating disk rheometer which, in various forms, has been widely adopted to measure the dynamic mechanical properties of a single specimen continuously during vulcanization. A profiled steel disk is embedded within a disk of the compound under study, and subjected to forced torsional oscillations. Values of torque and phase angle between torque and angular displacement are measured as a function of time of cure. The amplitude of oscillation is small, typically 1-3 degrees, and the frequency is typically 1.7 Hz.
Commercial rheometers are currently used for testing the cure properties of rubber compounds in laboratory samples. There are about twenty companies worldwide producing commercial rheometers. The largest producers of such apparatus are Monsanto Chemical Co., Instruments Group, Toyo Selki Selsolsu-Sho, Ltd., and Zwick of America, Inc. The commercial rheometer is a large, complex, stand alone off-line, lab only device wherein the sample holding portion of the machine is as important to the results obtained as the sensing arm which measures the torque of the oscillating disk. Consequently, the current commercial rheometer is also expensive. There is currently no known device for measuring in situ the cure status of a fully formed elastomeric product during manufacture.
It is an object of the present invention to provide a method and apparatus whereby the cure properties of a fully formed elastomeric article can be measured in situ in a mold to increase manufacturing efficiencies. It is also an object of the present invention to provide such apparatus on a much smaller scale and at 1/10 to 1/20 the cost of a commercial rheometer. Other objects of the invention will be apparent from the following description and claims.